The enantioselective synthesis of a new and extremely effective organoseleniumreagent (2) is reported. This chiralreagent was found to react with alkenes with a very high degree of facial selectivity in selenomethoxylation and ringclosurereactions. In some cases the diastereoselectivities were found to be as high as 98%.
Capricious Stereoselectivities of Alkenylpotassium Formation under Kinetic and Thermodynamic Control Oxygen-Triggered Configurational Equilibration of an Allyl Type Organometallic Compound
(E)-isomers, no matter in which configuration the resulting organometallic is thermodynamically more stable. A striking illustration is given by (Z)-4,4-dimethyl-2-pentenyl potassium which is formed 15 times faster than its (E)-isomer, although the latter is clearly favored under equilibrium conditions. The configurational reorganization of alkenylpotassiumcompounds in tetrahydrofuran solution is very
Enantioselective Hydroamination of Alkenes with Sulfonamides Enabled by Proton-Coupled Electron Transfer
作者:Casey B. Roos、Joachim Demaerel、David E. Graff、Robert R. Knowles
DOI:10.1021/jacs.0c01332
日期:2020.4.1
proceed via N-centered radicals formed by proton-coupled electron transfer (PCET) activation of sulfonamide N-H bonds. Non-covalent interactions between the neutral sulfonamidyl radical and a chiral phosphoric acid generated in the PCET event are hypothesized to serve as the basis for asymmetric induction in a subsequent C-N bond forming step, achieving selectivities of up to 98:2 er. These results offer
报道了一种对映选择性、基于自由基的方法,用于烯烃与磺酰胺的分子内加氢胺化。建议这些反应通过磺酰胺 NH 键的质子耦合电子转移 (PCET) 活化形成的 N 中心自由基进行。中性磺酰胺自由基与 PCET 事件中产生的手性磷酸之间的非共价相互作用被假设为后续 CN 键形成步骤中不对称诱导的基础,实现高达 98:2 er 的选择性。这些结果进一步支持了非共价相互作用在瞬态和高反应性开壳中间体的反应中增强立体选择性的能力。
The copper(<scp>I</scp>)-catalysed coupling of Grignard reagents with 5-lithio-2,3-dihydrofuran and 6-lithio-3,4-dihydro-2H-pyran
The organocuprates derived from reaction of Grignard reagents with CuBr·Me2S react with 5-lithio-2,3-dihydrofuran and 6-lithio-3,4-dihydro-2H-pyran via a 1,2-metallate rearrangement to generate an alkenylmagnesium cuprate.
Enantioselective Bromocyclization of Olefins Catalyzed by Chiral Phosphoric Acid
作者:Deshun Huang、Haining Wang、Fazhen Xue、Huan Guan、Lijun Li、Xianyou Peng、Yian Shi
DOI:10.1021/ol202527g
日期:2011.12.16
A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various cis-, trans-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee.